Recently, a process has been implemented where a learning value obtained through vehicle control is stored in a nonvolatile memory at the end of controlling a vehicle system and the learning value is then read from the nonvolatile memory and later to be used for vehicle control when the vehicle system is to be started. An EEPROM (Electronically Erasable and Programmable Read Only Memory) is preferably used as the nonvolatile memory. A CD-R, a CD-RW, a DVD-R, a DVD-RW, a hard disk, etc. may also be used as the nonvolatile memory.
In an information management apparatus which utilizes this type of process, data of the learning value may be stored partially in a case where an accident such as a power shutdown or the like occurs when the data is being stored in the nonvolatile memory. As a result, a problem occurs in that it becomes impossible to use the learning value which has been collected.
This problem occurs especially in a case where the information management apparatus is mounted on a vehicle. In this case, a battery of the vehicle is replaced by a user of the vehicle or a repair shop shortly after the vehicle is stopped. As a result, a writing process of a data block of the nonvolatile memory may not be completely finished. A similar problem may occur not only in the case where the apparatus is mounted on the vehicle, but also in the case where there is an apparatus or a system, such as a cellular phone or the like, where a battery is detachable.
In this connection, an invention of an information management apparatus in which data is stored in both a management area sector and a backup sector that are formed in a flash memory is disclosed (see, e.g., Patent Document 1).
According to this information management apparatus, when update data is written into the apparatus, data stored in the backup sector is deleted first, and then a copy of the data stored in the management area sector is written into the backup sector. Further, the data stored in the management area sector is deleted after a signature of the management area sector is cleared, and finally the update data is written into the management area sector. A signature is written into the management area sector when the update data is written into the management area sector.
When the data is read from the flash memory, it is determined whether the signature written in the management area sector is correct or not by comparing the signature with fixed data. If the signature is not correct, it is determined whether a signature written in the backup sector is correct or not. In a case where only the signature written in the backup area is correct, the data stored in the backup sector is written into the management area sector (see FIG. 9 of the patent document 1).
An invention of a data duplexing system in which data is written and stored into a master memory apparatus and a slave memory apparatus is disclosed (see, e.g., Patent Document 2). This system includes a status table in a control apparatus. A writing flag is set in an area of the master memory apparatus in the table when the data is being written into the master memory apparatus. A written flag is set in an area of the slave memory apparatus in the table when the data is being written into the slave memory apparatus. The duplexing system detects an accident when the data is being written in a state where the flag is set in the area of the master memory apparatus or the slave memory apparatus.    Patent Document 1: Japanese Laid-Open Patent Application No. 2008-71223    Patent Document 2: Japanese Laid-Open Patent Application No. 2006-79522